Tuning fork generator



April 18, 1933. A. L. MATTE TUNING FORK GENERATOR Original Filed June 16, 1928 with particularity in the appended claims,

Patented Apr. 18, 1933 UNITED STATES {PATENT orric ANDREW L. MATTE, OF SUMMIT, NEW .iEEsEmnssIGNoE TO AMERICAN TELEPHONE AND TELEGEAEH COMPANY, A CORPORATION OF NEW YORK TUNING FORK GENERATOR Original application filed June 16, 1928, Serial No. 286,042. Divided and this application filed May 15, 1930. Serial No. 452,642.

This invention relates to tuning forks and tuning fork generators, and more particularly to arrangements for producing current of the frequency of vibration of a tuning fork or of some harmonic of its frequency of vibration.

This is a division of a copending application, Serial No. 286,042, filed June 16, 1928.

In general, the vibration of a tuning fork may be made to generate an alternating current in two distinct ways. First, the vibrathese two methods will be readily appar out if one .recalls that the electromotive principles underlying the two methods enumerated hereinabove will be employed in connection with the invention to be subsequently described.

One of the primary objects of this invention is to generate an alternating current by the continuous action of a tuning fork, the tuning fork being electrically driven.

Another object of this invention is to prevent the electrical driving means of the tuning fork generating arrangement from affecting or interfering with the generating action.

\Vhile this invention will be pointed out the invention itself, both as to its further objects and features will be better understood from the detailed description hereinafter following when read in connection with the accompanying drawing, in which Figure 1 shows how the number of effective turns of a coil of wire may be periodically changed; Fig. 2 shows how the flux threading a coil of wire may be periodically changed; and Figs. 3 and 4 show how to produce an. alternating current from a tuning fork energized from a local source, so arranged that the driving flux may have substantially-.110 efiect upon the circuit in which the current is generated.

Referring to Fig. 1 of the drawing, there isshown a tuning fork F having two tines or prongs P and P The tuning fork may be mounted very solidly on a rigid, heavy base which is supported on a soft, diffused bed such as may be provided by pads of rubber. This fork may be made, preferably, of ordinary soft steel although it will be clear that it may be made of any well known magnetic alloy.

A coil of wire W wound on a core of iron R is placed between the tines or prongs P and P a considerable distance away from'the free ends of these tines or prongs. The current that may flow through the winding W is supplied by a local source of direct current such as is designated as B,. One terminal of the source B is connected to a contact D, while the other ter minal of this source is connected to the winding W When contact K is closed, current will flow from the source B through the winding W and over the curved portion of the tuning fork F between contact K and the fixed contact D.

The tuning fork F may be started by pulling the prongs P and P together, i. e., inwardly. After being started, it is driven continuously, the energy for its continuous operation being supplied from the source B The contact K provides a make-andbreak circuit which periodically interrupts the direct current flowing from the source B Thus, after the prongs P and P have been drawn together, the contact K will be opened so that no current may flow from the source B through the winding \V As these prongs become released, soon the contact K will become closed and current will then flow from the source B through wind ing Accordingly, that winding will become excited and its core will become threaded with a dense magnetic field. The prongs P and P will then be attracted, thereby opening the circuit including the source B and the winding \V, at the contact K. Later, contact K will be closed and another pulse of current will surge through the winding W and the prongs P and 1? will be attracted, i. e., drawn inwardly again. And, so it continues.

Another core of magnetic material is placed adjacent to the free ends of the prongs P and P this core being so spaced from the free ends of these prongs that gaps J 1 and J respectively, are established. A coil of wire V is wound about a portion of the core R adjacent to one of the prongs such as P Coil W has a plurality of turns of wire so spaced that the length of the coil in the direction of its axis is about equal to, and no greater than, the corresponding dimensions of the adjacent prong P,. The winding W is connected to an output circuit S.

As the tuning fork F vibrates, a magnetic field is intermittently established by winding W,, as has been explained hereinabove. A portion of its magnetic flux will flow through the rounded portion of the fork F (which is at the left of the winding W Another portion of this magnetic field will flow over the prongs P and P and over the iron bar or core R As the fork F vibrates, the magnetic field passing through the bar R will intermittently cut more or less of the turns of wire of coil V In other words, as the fork vibrates, the number of effective turns of the winding W will be continuously changed and, consequently, an electromotive force of varying magnitude will be established across its terminals. Consequently, an alternating current may flow through the circuit S, the frequency of which will have a component equal to the frequency of vibration of the fork F. An alternating current is thus produced by virtue of the continuous change in the number of effective turns of the coil of wire W even though the flux through the core H were to remain constant.

In the usual arrangement for generating an electromotive force by a tuning fork, the flux threading a coil of wire is variable while all of its turns remain in the path of the threading flux. This is illustrated in Fig. 2. In this arrangement, a core of iron R is placed between the prongs P and P of the fork F so that gaps J 3 and J; are respectively established between prongs P and P and W and which )asses through the wron s P and P is similarly changed. hen prongs P and P are at their. extreme outer positions, i. e., when prongs P and P are the greatest distance apart, the reluctance of the magnetic path is a maximum. On the other hand, when these prongs are at their extreme innner positions, i. e., when these prongs are at their least distance apart, the

reluctance of the magnetic path is a min1-' mum. Since the winding W is in the path of a periodically varyingmagnetic flux, the voltage across the terminals of'winding W will also vary periodically, this voltage changing from a maximum positive value to a maximum negative value: Accordingly, an alternating current may flow through the circuit S which is connected to the winding V In this arrangement, it will be apparent that while the effective number of turns of the coil V remains constant, an alternating current may be produced by virtue of the periodical change ofthe reluctance of the magnetic circuit threading the winding or coil W I In the arrangements. ofFigs. 1 and 2 it will be evident that the wave shape of the electromotive forces produced in windings V and V respectively, are conditioned not only upon the vibration of the fork, but to an equal extent upon the'variations of the driving current in windin lV- Figs. 3 and 4 represent a top 'view and an end view, respectively, of an electrically driven tuning fork arrangement for producing an alternating current by virtue of the vibration of the associated tuning fork. In this arrangement, the flux produced by the electrical driving apparatus is divided and split up into two substantially equal parts which are made to oppose and neutralize each other in the generator windings, thereby preventing the fluxes produced by the winding IV, of the electrical driving apparatus from affecting the current generating action as will be apparent from the following description. This represents one of the important features of this invention.

The circuit arrangement for maintaining the tuning fork in continuous vibration after it is started, is shown in Fig. 3 in which reference characters similar to those of Fig. 1 have been employed to designate similar parts. The arrangement disclosed by Figs. 3 and 4 is designed to minimize the effect r these yokes in equal amounts.

thatlthe flux established by winding may have upon the nature of-the current generated by the system and flowing through the output circuit S, assuggested hereinabove. Here, two similar yokes of magnetic material R and R are placed adjacent to the prongs P and P of the fork F. The yokes R and R areso placed with respect to the pr ongs P and P that gaps J and J, are established between these yokes and prong P and gaps J and J are similarly established between these yokes and prong P The free ends'of the prongs P and P will periodically alter the cross-section and mean length of the effective magnetic path designated in Fig. 4 by the dot-and-dash line, thereby periodically changing the re luctanoe of this magnetic path.

Coils V and W are wound, respectively, on yokes R and R and are connected in series-relationship. A battery B connected in series relationship with a choke coil L, supplies current to the windings W and for their energization, the choke coil L being interposed so as to prevent the alternating current generated by the system from becoming shunted through the battery B A condenser C, preferably of large capacity, is connected in series with the output circuit S in order that none of the direct current from battery B may reach output circuit S, this condenser, nevertheless, permitting the alternating current generated in windings W and to readily flow therethrough.

As the fork F vibrates, the reluctance of the magnetic path, including yokes R, and R and gaps J J J and J 8 becomes periodically changed, as has been stated hereinabove. Accordingly, electromotive forces are generated in windings V and Since these windings are series aiding, the electromotive forces generated thereby will be additive in effect and will result in the transmission of a current of corresponding frequency through condenser C to the output circuit S. Very little of this current can be shunted through the circuit of battery B by virtue of the presence of the choke coil L.

The magnetic circuit established by the driving apparatus, i. e., that magnetic circuit produced by winding W shown in Fig. 3, will be substantially without effect upon the voltages generated by windings W and and therefore without effect upon the wave shape of the corresponding current transmitted through the output circuit S. The magnetic field established by winding K which flows through the prongs P and 1? also divides between the yokes R and R By making the reluctance of these two mag netic paths equal, the magnetic field established by winding W will pass through In other words, the fluxes-in the yokes R and- R due to the magnetic field established by winding W are substantially equal and the directions of the fluxes through yokes R and R are in mutually opposite directions. Accordingly, these fluxes will tend to produce mutually neutralizing 'eleetnoniotive forces and hence be substantially without effect upon the generation of the electromotive forces impressed upon circuit S.

\Vlu'le this invention has been shown in certain particular embodiments merely for the purpose of illustration, it will be understood that the general principles of this in vention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

- What is claimed is:

1. The combination of two U-shaped cores of iron, the ends of which face each other, a tuning fork placed so that each prong will be between the adjacent ends of both of said U-shaped cores, each prong of the tuning fork being spaced by equal gaps from the adjacent ends of both said U-shaped cores, two coils of wire wound on said U-shaped cores and arranged in series relationship so that their magnetic effects which produce alternating currents will be additive, and means for producing a driving flux for said tuning fork which threads said U-shaped cores equally in order that the effect of said flux will be negligible.

2. The combination of a tuning fork, means for driving the tuning fork, two electromagnets having Ushaped cores of iron positioned on opposite sides of the two planar surfaces bounding the faces of the fork, each end of each U-shaped core being closely adjacent to one of the prongs of the fork, each-end .of each U-shaped core being spaced from the corresponding prong by a small gap, all of said gaps being substantially equal, and a source of direct current connected in series with the windings of said electromagnets.

3. The combination of a tuning fork, means for producing a flux for driving the fork, two U-shaped iron cores on opposite sides of the prongs of said fork each having a coil of wire wound thereon, the ends of each U-shaped iron core being separated from both prongs by equal gaps, said U- shaped iron cores being equally threaded by the driving flux, and a source of direct current connected in a circuit in series with the coils of wire wound on said U-shaped iron cores.

4. Electrical generating apparatus comprising the, combination of a tuning fork, a core of iron having a coil of wine wound thereon which is positioned between the prongs of the fork, the axis of said core being perpendicular to the prongs of the fork,

a source of direct current, and two similarly shaped iron bars both equally spaced from the ends of both of the prongs of the fork and parallel to the core upon which said coil '10 tuning fork, two similarly shaped bars of iron both equally spaced from the ends of both prongs of the tuning fork, each bar of iron having a coil of Wire wound thereon, equal portions of the driving flux passing through the bars of iron upon which the coils are wound, and means for supplying direct current to said coils of wire.

6. The combination of two U-shaped cores of iron the ends of which face each other,

to the other and similarly separated therefrom by air-gaps, each of said iron cores diverting some of the driving flux therethrough, a winding mounted on each of said iron cores, each winding having a number of turns such that the electromotive force caused by the driving flux passing through one of the iron cores will equal the electromotive force caused by the driving fiux passing through the other iron core, a source of direct current, said windings being connected in series with each other and with said source of direct current so as to produce a second flux which results ,in the generation of an alternating current as the second flux is varied by the motion of the tuning fork.

In testimony whereof, I have signed my name to this specification this 13th day of a tuning fork placed so that both of its prongs will be adjacent to both ends of each of said u-shaped cores, each prong of the tuning fork being spaced from and between the corresponding ends of both U-shaped coresby-equal gaps,means for driving the tuning'fork, a source of direct current, and coils of wire wound about said cores of iron and connected in series relationship with respect to said source of direct current.

7. In an electrically driven tuning fork generator, means for preventing the driving flux from afiecting the wave shape of the generated current, said means comprising two separately excited generator coils mounted on individual cores, said cores being so disposed as to cause the interfering flux to divide into twoequal amounts which thread'them in mutually opposite directions.

8. In an electrically driven tuning fork 49 generator having a driving magnet and a separately excited generator arrangement including two separate cores, means to prevent the driving flux from affecting the wave shape of the generated current, said means consisting of means for causing the driving flux to separate into two parallel paths formed by the two generator cores, the component fluxes of the driving flux setting up equal and mutually opposite electro- 59 motive forces in said generator cores.

9. In an electrically driven tuning fork having separately excited generator windings, two cores upon which the generator windings are wound, said cores forming parallel opposing paths for the stray magnetic field emanating from the driving means of the tuning fork and forming seriesaiding paths with respect to the generator flux.

00' 10. In a tuning fork generator driven by a magnet, the combination of an iron core bridged from one of the tines of the fork to the other and separated from these tines by air-gaps, a second iron core similarly 65 bridged from one of the tines of the fork May 1930.

7 ANDREW L. MATTE. 

